Control systems for regulating the operation of mobile material distribution devices--including, for example, farm implements such as sprayers and planters, and public works vehicles such as salt spreaders--have been known in the art for some time. Such prior art control systems are usually used to control the rate at which material is dispersed or distributed from the material distribution device. Some such systems, for example, include microprocessor based control systems wherein the ground speed and field position of the material distribution device, as well as the type of soil and other factors, are continually monitored in order to distribute a controlled amount of material throughout the field.
Such prior art control systems, however, suffer from certain drawbacks. For example, prior art control systems frequently cause an inefficient loading and/or unloading of material from the material distribution device.
In particular, prior art control systems generally cause a misapplication of material when the outlet ducts or nozzles of the material distribution device are momentarily closed by the operator. For instance, when the material distribution device is turning around at the end of a field or is traveling across a section of field which should not be treated, the outlet ducts or nozzles of the material distribution device are momentarily closed by the operator in order to prevent the dispersal of material therefrom. This, in turn, causes some prior art control systems to fully open a product flow control valve which results in an over-pressurization of the product distribution line leading to the outlet ducts or nozzles, and also causes an over-application of material when the outlet ducts or nozzles are subsequently reopened by the operator. In other prior art control systems, an automatic override causes the product flow control valve to completely close which results in an under-pressurization of the product distribution line leading to the outlet ducts or nozzles. This under-pressurization, in turn, results in the loss of pressure and the development of air pockets in the product distribution line, and also causes an under-application of material when the outlet ducts or nozzles are subsequently re-opened by the operator.
Another problem associated with prior art control systems is that when the material distribution device is receiving a supply of material from an external supply source such as a nurse truck, an additional pump may be required for loading material into the product tank of the material distribution device. Such a set-up requires numerous plumbing connections which significantly increases the likelihood of material spillage and other accidents.